1. Field of the Invention
The present invention relates to a composite charged particle beam apparatus for irradiating a sample with at least two charged particle beams.
2. Description of the Related Art
A FIB-SEM composite apparatus is known as an apparatus for observing, through a scanning electron microscope, a cross-section subjected to etching processing by focused ion beam irradiation.
In SEM observation, in general, when an observation surface is observed from a direction perpendicular thereto, observation can be performed with a high resolution. Then, there has been proposed a sample processing and observation method for SEM observation of a cross-section formed by FIB processing from a perpendicular direction with the use of a composite charged particle beam apparatus in which a FIB column and a SEM column are arranged at a right angle (see JP-A-2011-196802). According to this method, the cross-section cut out by fine processing by FIB can be observed by SEM with a high resolution in situ.
By the way, in SEM observation, in general, when a working distance (WD) as the distance between an objective lens and a sample surface becomes smaller, observation can be performed with a higher resolution. Therefore, the conventional apparatus has been designed so that the tip of the SEM column and a sample may be arranged as close as possible to each other.
However, if the tip of the SEM column and the sample are arranged close to each other, there have been problems in that the tip of the SEM column may interfere with the tip of an ion beam column or a gas nozzle for film formation as other components and that charged particles or X rays generated from the sample may be prevented from reaching a detector.